The present invention relates to a ratchet wrench for selectively applying torque to a fastener.
FIG. 5 illustrates a prior art ratchet wrench 100. The prior art wrench has a wrench body 102 including a handle portion (not shown) and a head portion 106. A pawl 102 is shown in its gear driving position. In this gear driving position, the head portion 104 engages the pawl 102 so as to apply force to it during torque application is a xe2x80x9csidewardsxe2x80x9d direction of the pawl 102 (indicated by arrow F). That is, the force is applied mostly circumferentially with respect to the axis about which the gear 108 rotates. As a result, the force transmitted to the gear 108 by the pawl 106 tends to be focused at the teeth closest to the point of engagement. Specifically, the force is primarily focused at the outermost tooth of the pawl closest to the point of engagement. As a result, the remainder of the pawl teeth transmit considerably less force. This is an unsatisfactory load distribution.
One aspect of the present invention provides a ratchet wrench for applying torque to a fastener. The wrench comprises a wrench body having a handle portion configured to be manually grasped and a head portion providing a pawl engaging surface; and a ratchet gear constructed and arranged to be removably engaged with the fastener such that torque applied to the gear is transmitted to the fastener to affect rotation thereof. The ratchet gear is mounted to the wrench body such that the gear and the body are rotatable relative to one another about a gear axis, the ratchet gear having a plurality of gear teeth arranged on a radially outer peripheral surface thereof in circumferential relation with respect to the gear axis. A pawl is mounted to the wrench body and having a plurality of ratcheting teeth arranged in an arc essentially complementary to the gear teeth and a load receiving surface facing generally opposite the ratcheting teeth. The ratcheting teeth include a pair of outermost teeth provided at opposing ends of the arc and inner teeth therebetween.
The pawl has a gear driving position wherein the ratcheting teeth of the pawl are positioned for driving engagement with the gear teeth and the pawl engaging surface is positioned for driving engagement with the load receiving surface of the pawl such that a manual force applied in a first direction to the handle portion of the wrench body is transmitted from the wrench body to the pawl via the driving engagement between the pawl engaging surface and the load receiving surface and from the pawl to the ratchet gear via the driving engagement between the ratcheting teeth and the gear teeth so as to apply torque to the gear. The pawl is constructed and arranged with respect to the gear teeth and the pawl engaging surface such that, as the manual force is being transmitted to the gear via the pawl, the total amount of force applied to the gear is distributed among the ratcheting teeth in such a manner that an amount of force applied to the gear by each of the inner ratcheting teeth is greater than or equal to an amount of force applied to the gear by either of the outermost ratcheting teeth.
The wrench further comprises a biasing element engaged with the pawl and biasing the pawl to the gear driving position. The biasing element is constructed and arranged such that a manual force applied to the handle portion in a second direction opposite the first direction causes rotation of the wrench body relative to the ratchet gear with the ratcheting teeth of the pawl repeatedly ratcheting over the gear teeth against the biasing of the biasing element.
Another aspect of the invention provides a ratchet wrench for applying torque to a fastener. The wrench comprises a wrench body having a handle portion configured to be manually grasped and a head portion providing a pawl engaging surface; and a ratchet gear constructed and arranged to be removably engaged with the fastener such that torque applied to the gear is transmitted to the fastener to affect rotation thereof The ratchet gear is mounted to the wrench body such that the gear and the body are rotatable relative to one another about a gear axis. The ratchet gear has a plurality of gear teeth arranged on a radially outer peripheral surface thereof in circumferential relation with respect to the gear axis. A pawl is mounted to the wrench body and has a plurality of ratcheting teeth arranged in an arc essentially complementary to the gear teeth and a load receiving surface facing generally opposite the ratcheting teeth. The ratcheting teeth include a pair of outermost teeth provided at opposing ends of the arc and inner teeth therebetween.
The pawl has a gear driving position wherein the ratcheting teeth of the pawl are positioned for driving engagement with the gear teeth and the pawl engaging surface is positioned for driving engagement with the load receiving surface of the pawl such that a manual force applied in a first direction to the handle portion of the wrench body is transmitted from the wrench body to the pawl via the driving engagement between the pawl engaging surface and the load receiving surface and from the pawl to the ratchet gear via the driving engagement between the ratcheting teeth and the gear teeth so as to apply torque to the gear. The load receiving surface is positioned on or between two outer radial lines of four imaginary radial lines dividing the arc into five equal imaginary arcuate sectors.
The wrench also comprises a biasing element engaged with the pawl and biasing the pawl to the gear driving position. The biasing element is constructed and arranged such that a manual force applied to the handle portion in a second direction opposite the first direction causes rotation of the wrench body relative to the ratchet gear with the ratcheting teeth of the pawl repeatedly ratcheting over the gear teeth against the biasing of the biasing element.